The invention relates to a communications cable network in a duct or pipe system primarily used for other purposes in accordance with the preamble of claim 1.
DE 197 01 737 A discloses a method for installing optical fiber cables in accessible or non-accessible water, sewage, or rainwater ducts, or also gas pipes. This ensures that the fiber optic cables can be installed in simple manner all the way into the individual buildings without costly earthwork. The fiber optic cables are fastened to the inner wall of the ducts or pipes by means of straps using a remote control duct robot. The fiber optic cable used here has an outer metal protective tube holding the optical waveguides. Many such fiber optic cables can be fastened next to each other on the walls. The fiber optic cables can also extend within cable conduits, i.e. the cable conduits are first fastened to the wall and the fiber optic cable is subsequently pulled or blown into the cable conduit. A disadvantage of this method is that it requires two operations to install the fiber optic cable, namely installing the cable conduit and pulling in the fiber optic cable. As mentioned above, the fiber optic cables have an outer metal tube with good bending properties combined with good stability. Due to these good bending properties, the straps have to be spaced relatively closely, for example, at a distance of 1-2 m to prevent marked sagging by the cable. The good bending properties must make it possible for the cable, as it exits the conduit end enters the shaft in the case of a sewage pipe, to bend by 90.degree. within a relatively small space without kinking of the metal tube.